A 'number-slider' question cannot be marked as mandatory when displayed as a 'slider'

[MavromatisK]

Describe the bug
A 'number-slider' question cannot be marked as mandatory when displayed as a 'slider'.

To Reproduce
Steps to reproduce the behavior:

1. Go to the editor page of your survey
2. Add a 'number-slider' question to your survey
3. Click on your 'number-slider' element
4. Mark your question as mandatory
5. (By default the 'number' option is pre-selected in the display field)
6. In the display field, click on the 'slider' option
7. You are no longer able to mark your question as mandatory
8. Your 'number-slider' question is no longer mandatory

Expected behavior
A 'number-slider' question that is displayed as a 'slider' should be able to be marked as mandatory.

Screenshots

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Chrome
• Version: 89

Smartphone (please complete the following information):

• Device: n/a
• OS: n/a
• Browser: n/a
• Version: n/a

Additional context
n/a

[BRU-EUSurvey]

Hi there,
Thank you for the feedback.
Indeed, there is something to improve here.
This is a known issue. Originally, we have not offered the 'mandatory' option for slider as there is always a value set.
We aim now to add 'null' as original/default value and only set a value if/when the user has clicked somewhere on the slider.
In this way, we could have optional or mandatory sliders and this option would make sense.
Currently, there is always a value set (different from null), therefore, it does not make sense to have a mandatory slider.
Many thanks.

[BRU-EUSurvey]

Ticket 7297 created for this improvement.