Collective has a fixed size in the middle of the monitor - can i change it?

how can i change the position of the collective sites?
actually it is centered and very small, it doesn’t use the full size of my monitor.

can i change it without searching in the source code?

I don’t think this is possible for now. As far as I can see it is a limitation set in text-app (used by collecitves). In apps/text/css/styles.scss I found:

:root {
--text-editor-max-width: 670px

I would like to have a much wider page as well. Especially tables with many columns would look much better.
I think I found an corresponding issue: Configurable line-length for Editor · Issue #4024 · nextcloud/text · GitHub

You can use the CustomCSS app to add your own CSS rules to override the editor width like this:

:root {
    --text-editor-max-width: 960px !important;

.page-title, div.editor {
    max-width: 960px !important;
    margin: 0 auto;

However the UI code still assumes a fixed width of 670px and the table of contents will not work properly after applying this change. Maybe there is another fix possible to cope with that.