Add selecting box

[D-PALISSE]

Hi there!

Very usefull gem and i would start by thank you for your great job!

I'm looking for generate some selecting box with severals options of value by the user, i didn't see command for that and i'm asking if this is possible, and if is not, maybe you have planned to do this ?

Thank you for your attention :)

[Paxa]

Hello, it's not available at the moment, going to implement it later. Need to resync new changes in libxlsxwriter and may be add helper methods

Related #40

Thank you for feature request