I am writing markdown with sublime and want to type math equations faster. Is there anyway to achieve the following functionality in sublime snippet?

Type any character followed by a number, press tab and it will become character_number. For example, if I type ‘a1’ and press tab it will become ‘a_1’.

If this cannot be achieved by snippet, what about packages?

Put the cursor inside a file / folder / URL / word and run the command. It automatically expands the selection until it hits delimiter chars, which can be changed in the settings (see below).

certainlyakey starred leonid-shevtsov/SearchInProject_SublimeText

Jump between characters in Sublime Text 3 without using a mouse at ease

Autocomplete relative or absolute file paths in Sublime Text project folder

Based on the Xdebug protocol functionality in SublimeXdebug package by Kindari.

certainlyakey starred colinta/SublimeQuickFind

Sublime plugin that provides helpful color tooltips

This is a simple plugin that was created to save favorite files that are not part of a project. It can also be used to save and load groups of files which may be useful even for files part of a project.