This article explains the Multiple Selector block that can be added as a block to design an app.
https://youtu.be/zqMl8VbIHy0
Click on the block and start editing on the panel that appears on the right side.
This is what appears as the name of the input block to the end-user.
This is the text that goes below the input block to help the user.
List of options that appear in the multiple selector. Enter one option in a line.
Select one of Chips or Standard view.
[caption id="attachment_9905" align="alignnone" width="454"]
Chips view[/caption][caption id="attachment_9906" align="alignnone" width="507"]
Standard View[/caption]
Tick this option if you want the user to compulsorily fill the input block.
FAQ
Q: What is the variable value when I select multiple options?
A: If the user has selected multiple values as shown below
then the final value of the variable comes as "HTML,Java,Tally".
Hence the variable should be used as -