Slow motion playback just for editing

Note: This suggestion is ONLY about playback speed in editing, not the saved/exported/final version.

You can speed up playback by pressing L, and you can reverse that speed by pressing J. But once it hits the video’s fps, hitting J pauses and then reverses the play direction (playing in rewind).

I need a similar keyboard shortcut to play forward or backward at an fps speed of my choice (e.g. 3 fps). I’d like to be able to see what fps it’s playing at on the player pane and adjust it with both mouse cursor, by typing in a numeric setting, or pressing a keyboard shortcut to step or or down in speed.

I can hold the right/left keys for a slower playback, but I can’t set the speed of this, including stepping the speed up or down, and I can’t just hit a button once to play like this, I have to hold the button down.

Supposedly I can right-click the sequence in the project pane and select Modify > Interpret Footage and change things here, but for some reason this option is greyed out for my new sequence. I really just want the means to do this as easily as the L and J keys provide, and with on-screen indicators of this speed that I can modify.

Please also add this as a button to the Button Editor options for the clip player, in addition to the Step Forward/Backward 1 Frame buttons.