Godd afternoon to everyone and thanks for your replies.
I would like to ask you for help because I`m new with this great app. I would like to choose from a dropdown list, that appears at start of the app, an item, and based on my selection I need to show only the items that match with it and, if it is possible, not change the information shown unless I change the selection on the dropdown list.
You could use an Enum column in your user settings for the dropdown. Then, you could create a slice in your app that filters your data based on the user settings. The row filter for your slice would probably look like [Some Column] = USERSETTINGS("Your Enum Column"). You could make the slice (or the underlying table) read only.