The Trick:
Just press "A"
Also, you don't need to fill it up to activate it.
Source: https://steamcommunity.com/sharedfiles/filedetails/?id=2578177714
More Tetris Effect: Connected guilds
- All Guilds
- Settings to check out when starting + Small MP notes
- Misc Achievement Guide
- How to get SS rank (Savvy & Strong)
- How to revive yourself in Connected mode (if you get yeeted!)
- How to unlock Secret levels 1984/1989
- The Basics 1 [Stacking]
- Effect Mode SS Ranks