Do not load all projects in project jump box
In our installation we have more than 3000 projects. All of these projects are loaded in browser on each page every time you open any url and 90% of page content is html with project names. We use Favourite Projects Plugin https://www.redmine.org/plugins/favorite_projects which allows to reduce number of projects loaded in project jump box. But in Redmine versions 3.4 and 4.1 there are many great improvements of standard functionality (#23310, #31355) and only one little thing is missing.
I think that projects should be loaded in project jump box dynamically when user typing in search box. By default you can show only N first projects or don't show anything (only bookmarks and recently used projects from #31355).