[FEATURE] color current subexpression between brackets in preview

[userrand]

Description of the Problem

Sometimes I can feel a bit lost in a long formula. It would be nice to see in the preview where we are by adding color to that part of the expression in the preview

Description of the Solution

One possible solution would be to maybe use the fact that you can find the brackets that surround a part of the code (as the extension can highlight those brackets) to extract the text in between and surround it with {\color{red} (initial text here)} or some other color. Another command would undo the added code. However, if it is possible to decouple the code used for the preview from the code written by the user, then that might be better as the colored preview could maybe move automatically/dynamically with the user.

Additional