Better configuration for Slide Gesture thresholds

[KraXen72]

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Describe the feature request below
Currently, the new Slide gesture options (Swipe up to select on spacebar and swipe left on backspace) have too big of a trigger threshold. I use a Slide sensitivity of 40 until #410 is implemented, and by the time the swipe-to-delete gesture triggers, i'm almost out of screen space, only allowing to select a few letters for deletion.

I propose a new slider for the trigger thresholds (one slider for both delete slide-left & selection slide-up) which goes in 0.25/0.5 steps that get multiplied by the current slide sensitivity.

• it should be able to go below the slide sensitivity (0.25 - 0.75) and start again after at least 2.25 or 2.5.
• It also would require sufficient explanation or a succinct name
• Additionally, some sound/haptic, (possibly a popup message?) when the threshold is reached wouldn't be out of place (if sounds & haptics are on), to signify that the slide gesture has triggered. Yes this is a separate thing, but i felt like it's too small to warrant a separate issue. let me know if that's the case, i'll split it.

I considered a pure numerical slider like the others, and while it would work, there would:

• be a lot of "deadzone" - values below the current minimum swipe length are ineffective, since that triggers swipe letter
• the far end would have to go up into 120 or more to be effective, making the slider super finicky to set.

Two sliders (one for slide up threshold and one for slide left threshold) are possible, but unnecessary in my opinion. I'd love to hear other people's opinion on how to solve this! And most importantly, thanks @storvik for implementing this awesome feature!