When creating the CSV files for Netscans, the required headers are as follows
IP,displayname,hostgroup,properties
It may not be immediately clear, but there are only 4 total columns you'll use for these imports and all 4 columns are required. All of the desired properties you want to apply to a given device must exist in that 4th "properties" column.
In our netscan documentation here https://www.logicmonitor.com/support/creating-netscans we even have some examples of lines. You'll notice that the properties entries are encased in double quotes with the format of the "prop.one=firstproperty prop.two=secondproperty" with each pair being space delimited.
IP,displayname,hostgroup,properties
10.0.0.10,Device from CSV,New Target Group,"prop.one=firstproperty
prop.two=secondproperty"
10.0.0.11,Another Device from CSV,New Target Group,"prop.one=firstproperties
prop.two=secondproperties"
Depending on the spreadsheet editor you're using, you can combine the columns beyond the 4th into that singular column using a CONCATENATE or similar function. For MS Excel they document it here https://support.microsoft.com/en-us/office/concat-function-9b1a9a3f-94ff-41af-9736-694cbd6b4ca2 . This will allow you to format that "properties" column with multiple properties and values as well as including the needed double quotes around here.