Some considerable time was spent attempting to get an output from SIMBAD which contained the required information for use by SkyViewNGC. After being unsuccessful via various pathways, the 'Criteria query' pathway was found to be the closest to the desired response.
Almost certainly there is a better way to do this - but this is what worked here.
Previous to sending the query the 'Output Options' page was set up and saved...
Then the query was run in the 'Criteria query' page (with a search expression specifying declination below 55 degrees, NGC catalogue and major dimension > 5 arcmin)...
The output file from SIMBAD had this format...
The CSV format files produced are delimited by the ';' (semicolon) character. Note that the coordinates are combined into one column - as is the angular size. A console application was coded (C#) to parse this file and produce another CSV file delimited by a comma character. In addition the coordinates are parsed out and separated into two columns. For the angular size only the major dimension (arcmin) is parsed out and passed to the processed CSV file. The format in the final result file is as follows...
ID,TYPE,RA,DEC,MAGNITUDE,DMAJ
NGC 7209,OpC,331.2240,+46.5080,7.7,36.5
NGC 147,GiG,008.300500,+48.508739,9.5,12.59
NGC 185,Sy2,009.7414166775100,+48.3375099651800,9.2,11.48
Looking through the results reveals that there are actually 75 Messier objects listed - even though the SIMBAD filter specified 'NGC'. This - hopefully - means that all Messier objects with their major dimension > 5 arcmin have been included. There are no Caldwell objects listed - so a manual check of those against the list will be needed.
The list of NGC objects so obtained contains some 532 items theoretically visible from 34 degrees South latitude. However, due to tree cover this is reduced to 344 objects below +10 degrees in declination visible at least for 30 minutes or so. Longer exposure times are achievable for the 283 objects below -10 degrees declination.
So - even with the restricted view due to tree cover at the home location - there are apparently more than enough objects of sufficient size to be interesting targets in the Seestar S50s through the trees.
Of course - there is the extra factor of brightness to be taken into account. Encouragingly 191 out the 263 objects with magnitudes given are brighter than magnitude 10. The remaining 20 objects with no magnitude given are HII regions and open clusters - which probably is why they don't have magnitudes given.
On the down side, about 140 objects are open clusters - which tend to be of less interest than other objects. This leaves about 50 objects which are bright, interesting objects of sufficient size suitable for the Seestar S50s. Given the dearth of clear nights lately those 50 objects are more than enough to begin with.