How to add dropdown lists in Google Sheets?

First, select the desired column or range, click "Insert", and select "Dropdown list".

Alternatively, you may use Data validation to create a dropdown list. In this case, select the data range, click Data, and select Data validation.

In the right sidebar that pops up, click "+ Add rule". Select "Dropdown" as the criteria and add the values you want to be a part of your list. You can also choose a specific colour for each value. Once you have finished, click "Done", and you are ready to go.

Now, in the cells you’ve applied a rule to, there will be a dropdown list with the possible values. This is especially useful in documents filled by different people to ensure data cohesion. You can also use data validation to ensure several different data constraints are correct, such as dates, texts, or checkboxes.