I see that chassidim are makpid to wear a gartel during a siyum sefer torah. The Natei Gavriel (Hachnosos Sefer Torah)p. 111 writes this practice sorcing it from Shabbos 10,a and Shulchan Aruch 91:2.
My question is would it not also be fitting to wear a gartel anytime writing or even doing hagah when fixing, according to this.
I remember one Sofer that would always wear a gartel when writing, but I do not think this is the main spread custom. You might be able to differentiate between concluding a Sefer Torah which is a special occasion as similar to wearing a gartel during special kibudim during a bris etc...
What are your thoughts?