Re 1.:
yEd does not support all GEDCOM features, indeed it ignores most top-level tags except INDI, FAM, and NOTE. Moreover, it does not not support GEDCOM pointers except for associating NOTE records to INDI records and INDI records to FAM records.
I would guess that the top-level OBJE record is referenced in an INDI record somewhere else in your example file. Since yEd does not support pointers, you need to restructure your GEDCOM file for yEd to import the FILE tag information.
I.e. instead of using references along the lines of
...
0 @O3723@ OBJE
1 FILE C:/Desktop/TES-Medias/SPaul.JPG
...
0 INDI
1 OBJE @O3723@
...
you actually need to inline the OBJE record information like so:
...
0 INDI
1 OBJE
2 FILE C:/Desktop/TES-Medias/SPaul.JPG
...
Using the latter structure, yEd will add the information from the OBJE record as custom property value for the node that represents the INDI record.
Re 2.:
That very much depends on the actual structure of the GEDCOM tags in your GEDCOM file. E.g. for
...
0 INDI
1 OBJE
2 TITL image description
2 FILE C:/Desktop/TES-Medias/SPaul.JPG
...
the pattern (?s)1\s+OBJE.*2\s+FILE\s+(.+)$ together with the replacement $1 will work.
The pattern assumes that the FILE tag is the last sub-tag of the OBJE tag. If there are others tags after the file tag, the pattern has to be adjusted accordingly.
