It can be a pain to deal with lists, custom lists, and custom floats since I believe LaTex syntax is not as straightforward or comfortable to read and understand, for beginners like me, as some other mainstream languages are.
According to @Joseph and @Christian, that problem could be solved by creating custom environments or even changing some caption options and they are quite right. However, the presented syntax by @Joseph, and available at https://github.com/abntex/abntex2/wiki/HowToCriarNovoAmbienteListing, did not work at first attempt.
So I wanna share my experience in order to help those with similar problems. Just to remember, the main problem is that the labels were not being displayed when printing a 'listof' contents as depicted below.

To solve that, printing both labels and their correct counter value, I tried two approaches where both successfully solved the problem.
before applying any of the solutions you should be aware that I am assuming you wanna create a custom float and display it, its caption, and listing names correctly.
For this to work, a custom float needs to be created with de commands:
\usepackage{float}
\newfloat{chart}{}{locharts}
\floatname{chart}{Chart}
The first one will import your float package and the second one will create a new float called 'chart', the first parameter, and it will store it in a list file called 'locharts', last parameter. The middle {} is responsible to hold the float format option. For this example, you can leave it in blank since I do not want any special options for that right now. Finally, the command \floatname is just defining that the recently created float should be called 'Chart' with a capital letter.
After creating your custom float you can use two approaches, that I provide here, to change the label names when displaying the list.
For the first approach, you should use the code below.
%CREATE A NEW COMMAND TO HOLD THE LIST FILE NAME SO YOU CAN HANDLE AND MODIFY IT
\newcommand{\listofchartsname}{List of charts}
%CREATE THE LIST
\newlistof{listofcharts}{locharts}{\listofchartsname}
%INSERT AN ENTRY
\newlistentry{chart}{locharts}{0}
%CHANGE THE LIST DISPLAY NAMES
\counterwithout{chart}{chapter}
%CHANGE HOW THINGS WILL BE PRINTED
\renewcommand{\cftchartname}{Chart\space}
\renewcommand*{\cftchartaftersnum}{\hfill--\hfill}
What I believe to be important here is the fact that you are creating a command with \newcommand{\listofchartsname}{List of charts} to hold a variable name called 'List of charts'. That variable is then used to give a name to your list with the command \newlistof{listofcharts}{locharts}{\listofchartsname}. After that, \counterwithout{chart}{chapter} is being used to specify not to count chapters when incrementing your float counter.
The trick of this first approach is finally achieved with \renewcommand{\cftchartname}{Chart\space} and \renewcommand{\cftchartaftersnum}{\hfill--\hfill} that will be holding 'Chart\space' and \hfill--\hfill commands respectively. Both are called when printing the list that you have created with
\newlistof{listofcharts}{locharts}{\listofchartsname}
The results of manipulating, creating, a custom float with this approach is depicted in the Fig. bellow

which was produced by calling
\pdfbookmark[0]{\listofchartsname}{locharts}
\listofcharts*
Differently, the second approach is based on caption options, as suggested by @Christian. Before going to that I wanna share this link: https://mirror.hmc.edu/ctan/macros/latex/contrib/caption/caption-eng.pdf. It is the documentation of the 'caption' package that describes ways on how to customize your captions and listing options for them.
In order to use this second approach you only need to use the code
\usepackage[labelfont=bf, textfont=bf]{caption}
\DeclareCaptionListFormat{chartListFormat}{\hspace*{-30.5pt}Chart #2~--~}
\captionsetup[chart]{listformat=chartListFormat}
where the command \usepackage[labelfont=bf, textfont=bf]{caption}, for this example, is importing the package 'caption', to handle them in an easy way. The options 'labelfont=bf' and 'textfont=bf' are just specifying that both fonts, from all my captions labels and counter, should be boldly printed.
In order to change how labels will be shown when listing you need to change the caption listing format with the option 'listformat'. Among many approaches, this can be accomplished by creating a custom listing format with the command \DeclareCaptionListFormat{chartListFormat}{\hspace*{-30.5pt}Chart #2~--~}, where 'chartListFormat' is its name, \hspace*{-30.5pt} being some space to avoid things to get overlapped, and 'Chart #2~--~' being a string telling that it should print the name Chart followed by the #2, a parameter, that indicates the current counter value for one float from the list (this command is called for each element on the created floats list).
To set that options, the command \captionsetup[chart]{listformat=chartListFormat} can be used and it is specifying the option 'listformat=chartListFormat' for the custom float 'chart' that was created. This approach will lead to a list as shown below

which was produced by calling
\listof{chart}{Charts list}
I hope that those methods could help any of you that is having some trouble configuring captions for custom printing or when just configuring captions. I wanna also share this link: http://www.peteryu.ca/tutorials/publishing/latex_captions. It contains some good examples of how to customize your captions.
Chartas prefix to your chart numbers, why should it print it then? Apparentlyabntex2(which is a class not recommended here on TeX.SE by some of our Brazilian users) or some other package changes the caption settings fortablehowever such thatTable ...appears – Feb 04 '18 at 19:13classicthesisclass solution with a memoir-based class. AFAIK, this class is not recommended by some users (including me) for other things (ABNT is ugly by itself, code is messy, national rules for English shouldn't apply, etc.), but one things it doesn't do is "mess up with document structure". It just doesn't do that, unless you are doing that. Besides, here is a much simpler package calledabnt, you might give it a try. – Feb 04 '18 at 23:45