Right click on the Photos icon in your Pictures folder.
Choose: Show Package Contents.
Drag the Masters folder on the the Lightroom app icon or the Library window.
The Import Dialog box will show. Move or Copy to desired location.
Note: this will only take the Master files (the ones you imported into Photos) and not any Albums or tags you may have assigned.
Can this process be done with only selected files, as I only want to transfer about 900 files?
Will my editing from I Photo be preserved during the import to Lightroom.
Editing will not be preserved if its a raw file. If you export the file(s) as tiff files the the editing will essentially be preserved but not editable.
To select files from multiple Albums or Events I suggest you gather them into an album for the purpose. Select All > File Export [tiff].
Import the resulting files to Lightroom choosing either Move or Add option in the import dialog.
Would you do me a favor and mark this question s answered (assuming it is). It will make it easier for people who search with a similar question.
where would I cliques to mark this question answered?
you should see a "button" in the lower left of the responses.
Also, I did not mention earlier an option under the File Menu. It was introduced in 5.7 but I never noticed.
Of course this would probably apply to the entire image library but should anyone else be looking for a solution, here it is.