Nextcloud unified search window is small … So make it bigger;)
There is a discussion in community forum but for now, custome CSS may be helpful.
#header-menu-unified-search { max-width: 1000px; }
#header-menu-unified-search > div { width: 100%; }
#header-menu-unified-search > .header-menu__carret { width: 0%; }
The result looks like this:
Together with ElasticSearch full text index, and additional support for .drawio files, unified search is more useful now for me.