Hi, i am very sorry about the false alarm.
another author also created a “testpage”, with the same name, which was set to “index”.
issue resolved. thx
ok, i have found a solution.
maybe you can insert into core.
/* Stackable Tabs
--------------
If you have multiple tabs and, for example, the second tab has significantly more content than the first tab, the maximum space is still reserved for the container. That means if the first tab with little content is open, there could be 1000px empty below, just because another tab requires more space. This code completely hides the inactive tabs (including reserved space).
*/
div.wp-block-stackable-tabs .wp-block-stackable-tab-content div[hidden="true"] {
display: none;
}
