Do you use it through dplyr or you send raw SQL with DBI? I didn't use RMariaDB package, so I'm not sure what interface is used.
With dplyr I'm not sure what problem you have exactly, so it'd helpful to provide short snippet of what you are trying to do to make it clear.
For raw SQL you can use something like glue package that allows you to put value of a variable inside of the string that you can then send to your DB.