Creating Scenarios

There are many uses of scenarios that will let you have just one spreadsheet, instead of several versions than need maintenance.
One that may not be obvious, but I found very useful, was to create different Language versions of the same calculation sheet (in my case to be used in English, French and Spanish speaking locations of our company). In that case all labels and text cells were included in the scenarios and were switched to the preferred language when the user selected the appropriate scenario (I automated that part by using a drop-down list).

Unluckily, scenarios have sheet scope, not workbook scope, but how to overcome this is another story.

There are many uses of scenarios that will let you have just one spreadsheet, instead of several versions than need maintenance.
One that may not be obvious, but I found very useful, was to create different Language versions of the same calculation sheet (in my case to be used in English, French and Spanish speaking locations of our company). In that case all labels and text cells were included in the scenarios and were switched to the preferred language when the user selected the appropriate scenario (I automated that part by using a drop-down list).

Unluckily, scenarios have sheet scope, not workbook scope, but how to overcome this is another story.

Scenarios are a very useful tool when creating versions of the same spreadsheet, but you have to understand how they work to avoid pitfalls. Here are two of the rules that I learned hard way, and I now follow when using scenarios:

Rule 1
As changing cells select only those that contain constants. Any formulas will be converted to constants when the scenario is displayed, and the calculations may be lost. Instead, include all ultimate precedent cells as the changing cells; when the values of those change the resulting calculations will be updated as well.
Hint: I colour-code all changing cells to let the user know that these are "Input Cells" (I use light green background).

Rule 2:
If creating several related scenarios, consider including the same changing cells in all of them, even if some of them do not change in most of your scenarios. This will prevent forgetting those cells when switching from an atypical to typical scenario.

There are more tips on scenarios on this site as well as elsewhere on the internet so check them too.

Gregg:
You cannot really toggle the scenario, what you can do is only display a saved scenario. When you do this, whatever was in the changing cells of the selected Scenario will be replaced (overwritten) by the values saved within the scenario. While you cannot un-display the scenario, you can use undo to revert to previous status, i.e, before displaying the scenario.

If you need certain set of data to revert to after displaying other scenarios, you need to save that set as another scenario, may-be naming it a Stating Scenario.

If by toggle off the scenario you meant "How do I edit my data after displaying a scenario?" you can simply do that; what displaying a scenario means is that the values in the changing cells are recalled from the scenario, but you can keep editing them as well as the rest of the sheet as needed.

I will post another comment with hints on how to design a scenario and what to avoid.

Once I have created and saved a Scenario using the Scenario Manager in Excel 2019, how do I toggle off the Scenario so that I may revert back to the original workbook, with the ability to toggle that Scenario when desired?