In some cases it very useful and helps a lot to remember the hotkeys.
For example: just one key for three vertical align.

alt-a - align center, alt-a twice - align left, alt-a thrice - align right.
Another case:

d - copy, dd - arraydir, ddd - arraycircular, dddd - arraycurve
I think 4-tap hotkey is too much, but 1..3 is good enough.
All my multitap hotkeys for now:

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