Tab Lab uses the VexTab syntax that generally is quicker and easier to write than the ASCII tab syntax. The syntax can also be parsed to produce a musical notation at the same time as the tablature. A tutorial on VexTab syntax can be taken here and a helpful cheatsheet can be found here. Notably, VexTab is also free and open source. It's licensed under the MIT license with source code available on GitHub.
Unfortunately, hotkey functionality is broken, so clicking around the interface for more complicated or more thoroughly documented tabs can take extra time.