Different tools that could be useful

• Pokelt: Select and View Elements Based on Attributes FROM Elements (Place Similar, Select Similar, ...), Plus Much More
  PokeIt for MicroStation — Select and View Elements Based on Attributes FROM Elements, Plus Much More - MicroStation Blog - MicroStation - Bentley Communities
• Last Mile: Drawing tools, DGN Exporter, ...
  https://bentleysystems.service-now.com/community?id=kb_article_view&sysparm_article=KB0018872
• Migration Utilities: XIN, Excel tools, ...
  https://bentleysystems.service-now.com/community?id=kb_article_view&sysparm_article=KB0019187

And some more here: 

VBAs and DLLs for Custom Functions

Featurized Blogs for good references:

https://communities.bentley.com/other/old_site_member_blogs/peer_blogs/b/marc_thomass_blog