As a side note: One can copy&pase the content of such windows.
Also I tested the new version of the filter and for me it properly supported the file name even when I used the long name:
-> so replacing the VSFilterMod.dll might fix the issue for you too
Just to let you know how the output would have looked like when 8.3 filename support was enabled for that drive:
Note the "ASS_S~1.ASS" in front of the long name, that would be the 8.3 file name. 
Cu Selur
Also I tested the new version of the filter and for me it properly supported the file name even when I used the long name:
clip = core.vsfm.TextSubMod(clip=clip, file="F:/TestClips&Co/files/Subtitles/ass subtitle/(字幕备份 ass+srt+sup) 庆余年S01 Qing.Yu.Nian.S01.2019.V2.WEB-DL.1080p.AVC.LPCM.2.0.Mandarin@xixihaha - V2.ass")Just to let you know how the output would have looked like when 8.3 filename support was enabled for that drive:
C:\Users\Selur>dir /x "f:\TestClips&Co\files\Subtitles\ass subtitle\(字幕备份 ass+srt+sup) 庆余年S01 Qing.Yu.Nian.S01.2019.V2.WEB-DL.1080p.AVC.LPCM.2.0.Mandarin@xixihaha - V2.ass"
Datenträger in Laufwerk F: ist Stuff
Volumeseriennummer: CCD7-3F69
Verzeichnis von f:\TestClips&Co\files\Subtitles\ass subtitle
26.02.2021 14:54 1.048 (ASS_S~1.ASS (字幕备份 ass+srt+sup) 庆余年S01 Qing.Yu.Nian.S01.2019.V2.WEB-DL.1080p.AVC.LPCM.2.0.Mandarin@xixihaha - V2.ass
1 Datei(en), 1.048 Bytes
0 Verzeichnis(se), 1.389.350.760.448 Bytes freiCu Selur
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Dev versions are in the 'experimental'-folder of my GoogleDrive, which is linked on the download page.
Dev versions are in the 'experimental'-folder of my GoogleDrive, which is linked on the download page.