You can export a single range from the timeline by pressing the R key, dragging across the range and exporting. This can be within a clip, across clip borders, or multiple clips in a contiguous range. Both audio and video will be exported.
You can export multiple ranges from multiple clips in a single batch operation from the Event Browser by marking those with CMD+click+drag, then File>Share x clips. Example: https://larryjordan.com/articles/final-cut-pro-x-10-4-4-batch-export/
Using a free utility from frame.io you can export multiple clips from the timeline: https://www.provideocoalition.com/batch-export-clips-from-final-cut-pro-x-timelines/
Any clip in the timeline should normally already exist in the Event Browser. You can find those by selecting the timeline clip then doing SHIFT+F.
If the timeline was encoded externally then imported to FCPX you could blade the regions you want to save in the Event Browser, then File>New>Compound Clip.
If you want to save multiple clips from the timeline in the browser as a single clip without rendering, select those clips and do File>New>Compound Clip.
Note to change between select tool, range tool, trim tool, etc, you can just hold down the appropriate key and it will temporarily stay in that mode while you depress the key. The tool pop-up menu is in the top-left corner of the timeline: https://support.apple.com/kb/PH12532?locale=en_US
In general with FCPX it’s good to first start managing material in the Event Browser, mark favorites/rejects/keyword ranges, filter what you want, and only then proceed to the timeline. You can mark and navigate between multiple clip ranges in the Browser: https://support.apple.com/guide/final-cut-pro/set-multiple-ranges-in-the-browser-veradbf2dce/mac