1 - Plotting: miro.com
(Free)
This is brilliant - really, really fantastic. Highly visual, hugely customizable, excellent for plotting.
2 - CSIDE - specifically developed for writing in choicscript, this will save you huge amounts of time and is very well supported
(Free)
3 - Dashingdon - one of the simplest ways for a newbie to see what their story will look like, and share it with beta-testers. Great support
(Free)
4 - Choicescript tutorial
(Free)
This is an amazing resource - check out the sections on structuring your story
5 - Code writing shortcuts: https://textmechanic.com/
(Free)
e.g Add prefix : Add Prefix/Suffix into Line - Text Mechanic
You can add a prefix and a suffix to a list of variables copy pasted into the program. It is much quicker when generating multiple variables for your startup.txt file, that use a similar stem to variables you’ve used before.
6 - Map generator: Azgaar's Fantasy Map Generator
(Free)
Fun tool to stimulate your worldbuilding ideas. You can generate and edit maps, and the about section seems to say you own the writes and can sell them (ie include them in a game, maybe with a filter to make it look more unique)