Sorry if this is obvious but I am very much a beginner with LR
When I export a RAW picture as a jpeg with the save set to the same folder it does not appear on screen, either in the group view or the filmstrip along the bottom of the LR window - whether LR is set to Library or Develop.
I have checked, using Finder in my Mac and the jpeg is in the folder. What do I have to do to get the jpegs to show?
You have to add the exported jpeg back into the catalog. There is a setting in the export dialog in the Export Location setting labelled "Add to This Catalog", by default this is unchecked (probably most people don't bother adding the exported file back into the catalog, as they deem it unnecessary). So if you want to see the jpeg in the catalog you need to check that setting when you do the export.
Obvious when you know! Just tried it and it works fine.