Start by hovering over the floor-plan point or line segment you wish to edit using the reticle (cross-hairs). Once on target, the item will turn red, indicating the point/line can be moved / edited / or labeled.

Additionally, you can elect to add a new point to any floor line segment and then hover over the new point or line segment to highlight.
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While keeping the item highlighted (red), use the main middle white CAPTURE button, and press & hold to pick up the placed point. Move your device to re-position the point.  Once satisfied, release CAPTURE button to lock in place.

Line segments can be modified in similar fashion. Hover over any floor segment. Press & hold CAPTURE button to pick up & release to place.

When adjusting points in 3D mode, an additional segment & point is automatically added to your room model, so the floor, wall, and ceiling move in unison. Points & line segments can be moved in both 2D & 3D.