This option should allow to place 2D objects that will cover tripod, mostly present in nadir (bottom of clip), sometimes above (zenith) when camera is mounted to some lamp.
Such cover can be a externally prepared graphic (logo or artificial generated and retouch tripod replacement with surrounded pixels) or generated cover (one color circle, mirrored rest part of the clip, blurred or pixelized circular area).

So how the effect dialog could look like? - See image below.

Considering dialog illustration:
Type: for example provided image
X: relative to nadir/zenith (upper center position) x coordinate (+/-) (center of provided cover type)
Y: relative to nadir/zenith (upper center position) y coordinate (+/-) (center of provided cover type)

X and Y relative position corrections are sometimes required as tripod may not be visible symmetrical in nadir or zenith pole.

other not presented parameters:
Scale: rescale of cover image
Radius: radius of effect (for other than image)
Pixel size: for pixelization effect

Possible options for Type (bold font - most expected, green font - would be nice to have this too):

• provided image file
• blurred circular area with provided radius
• pixelized circular area with provided radius and pixel size (or some additional patterns)
• mirror effect (reflects rest of the clip frame (like putting convex mirror in place of tripod))
• one color circular area with provided radius
• concentrically placed text (provided radius of concentration, font size (should warn if text fits in such circle, or some preview window), font color, font type, auto generated movie time) - T3020.

A few layers of effect can be applied for both nadir and zenith and may change across the time.

How do I deal with that now?

1. Well cover logo is prepared in Inkscape (text to path (circle))
2. Export to PNG.
3. Open movie clip in VLC
4. Take screen shot.
5. Open screen shot in GIMP (with installed G’MIC plugin: https://gmic.eu/) - so can be related with T6395.
6. GIMP > Filters > G’MIC-GTK > Deformations > Equirectangular to nadir-zenith > “to nadir-zenith” (would be welcome if kdnlive would present such view in effect window allowing to (preview) position of the cover.
7. Making new layer with same size as image.
8. Opening cover file, positioning cover file and integrate with new transparent layer.
9. Make clip layer invisible (but with default options only one selected layer should be used by filter, so select that new layer from point 7 with 8).
10. GIMP > Filters > G’MIC-GTK > Deformations > Equirectangular to nadir-zenith > “to equirectangular”.
11. Export to PNG.
12. Add to kdenlive clips.
13. Add as track above others
14. Apply transparency options, so PNG transparency will allow to see clips from tracks below, with only cover visible on top of clips from lower layers.

So as you may see it is very complex process now, imagine you need to adjust the text, now…. ;)

As a result there should be generated final frame, that can be modified by sphere rotation effect (transformation of equirectangular projection).