Steps
Add the next knockout stage
Zones route teams into the next knockout stage of the same competition. In Schedule, choose New stage, set Stage type to Knockout and tick Create an empty playoff target. No teams or fixtures are generated.
Turn on rank zones
Select Edit on the group stage and tick Use rank zones. On a brand new stage the same editor appears in New stage, and New stages always save zones as a draft.
Add a zone for each range of places
Choose Add zone, keep Count from on Top and set From and To. In an eight-team group, places 1 to 2 can enter at Semifinal and places 3 to 6 at Quarterfinal.
Label and color each zone
Give each zone a Label and a Color. Colors are not a fixed palette: use any #RRGGBB or #RRGGBBAA value.
Save and check
Untick Save as draft and choose Save stage. Reopen Edit: the status reads Validated configuration and the summary shows the configured places with No teams moved.
Mark the bottom places if you need to
Set Count from to Bottom, From 1, To 2, and Designation to Relegation. It is display only, with no league membership changes. The Standings tab shows the bands.
Fix overlaps
Zones cannot share a place. In a six-team group, places 3 to 6 overlap the bottom two: the editor names the group and the places, and Save stage stays disabled.
Preview, then apply
When every fixture is finished, choose Preview qualification. It lists the Qualifying entrants and Planned fixtures. In the eight-team example, 3 plays 6 and 4 plays 5, and the bottom two stay out. Apply this preview creates the fixtures.
Saving a rule never advances teams. Only Apply this preview does.