You can still use the Test window even if the input field box is very small (it does happen when the name of some field is a little long). It is tricky because you can't really see what you are entering but it does work. You can then check the values correctness after pressing the Add Row button.
Alternatively you can score new data directly in Builder or if you want to use Analytics Manager, you can then create a Thing that will represent the entity that receive data, then create an analysis event linked to this thing. In that case you will be able to update the relevant Thing property more conveniently.
Both method of scoring (Builder or Analytics Manager) are demonstrated in the videos at https://community.ptc.com/t5/IoT-Tech-Tips/How-to-score-new-data-with-ThingWorx-Analytics-8-3-x/m-p/... .
The video works on standard non time series model but the principle is exactly the same for scoring. The only difference is that for time series you need to provide enough data to fill the lookback window . See https://www.ptc.com/en/support/article?n=CS293493 .
Hope this helps