If it were me, I would take that text file, and import the data into excel... and hopefully the data for the chrome extensions includes the NETBIOS or FQDN in it.
Then I would create a report/SQL query to give me the assetname, FQDN, and AssetID, then export the results as CSV or Excel.
Then I would order both by assetname or FQDN, sort them the same, and then compare/match-up the two spreadsheets (however you wish to do that - they make apps that compare - like beyondcompare)
then I would use the concatenate excel command to generate my SQL query to INSERT INTO the lansweeperdb, set custom10 or whatever field you have for it... =(C1) or whatever field you have the data in on the spreadsheet... WHERE ASSETID=(D1) or whatever field you have it in your spreadsheet...
So then when I have the syntax right in the concatenate result, I would take one single row, and try it in SQL Query Analyzer... (start with a select before you INSERT!) ... and verify the results...
If it looks good, then copy/paste all the concatenate column results into Query Analyzer, then run it..
Then you're done...
I'm not a DBA or data import/export expert, but remember, it's MS SQL back-end, so anything you can do in MSSQL, you can do -- just note you might mess up your data, so make a backup of the DB if you don't know what you're doing...
***and also note, anything you do in SQL behind-the-scenes isn't supported by Lansweeper Support**!