R Shiny DataTables with column filters - preserve the styling

I use the DT package in Shiny and want to use filters, however I have a problem with the styling of the filters:

Code: DT::datatable(overview,editable=TRUE, rownames=FALSE, selection='none', filter='top')

This is the way my DT looks when I add items. When I leave the dropdown, it looks like the following picture (collapsed) which is of course pretty bad.

I want to preserve the styling with the grey box and not have anything like "[..." for my users. How can I do this? If that is not possible with DT, using another package is also an option for me.

Edit: Reproduceable example

df <- data.frame(a = c("a", "a", "b", "b", "c", "c"), b = c(1,2,3,4,5,6), c("A", "B"))
df <- setNames(df, c("A", "B"))

DT::datatable(df,editable=TRUE, rownames=FALSE, selection='none', filter='top')

Thank you!