Consider adding some filters to the qfield layers list in project properties

[nyalldawson]

For large projects, the layers table in the qfield tab of project properties becomes extremely hard to navigate. I'd love to see some filters added here, specifically:

1. A checkbox for "show visible layers only", which would hide any non-visible/checked layers from the list
2. A freeform "text filter" box, which would filter the table by matching against any part of the layer name / source.