The shortcut is demonstrated in my level speedrun of adventure grounds. It may have already been found by someone but I never seen it in any speedruns. It's pretty self explanatory. You can find the run here.

This is slower than Dooshbag's wallzip, and even slower than W1 TBMS. Practical for maybe glitchless.

That's what i was going for.

that trick is used in glitchless in the normal world (it's not in the WR run because 99% of the people that run this game hate glitchless)