Hi Jozef,
Thank you for the additional information.
Another option for you could be to set the height and the width of the smart-window component to percentage values like so:

smart-window {
	--smart-window-default-height: 50%;
	--smart-window-default-width: 50%;

Also in order for the window to be positioned in the center it must have certain values like percentages or pixels.
If its possible to create a code example that showcases the behavior from your last reply it will be best, so that we are able to give you a solution about it and to assess the use case.
Please, do not hesitate to contact us if you have any additional questions.
Best regards,
Yavor Dashev
Smart UI Team