When you enter a large amount of content in the the RTE in umbraco, the RTE extends to accomodate the quantity of content. This can result in a lot of scrolling of the whole screen, such that the RTE toolbar scrolls out of the viewport. This can make it painful to apply styles to content towards the bottom of the RTE as you have to scroll down, highlight the content and then scroll back up to the toolbar before selecting the required style.
Is it possible to limit the size of the RTE in Umbraco such that the RTE scrolls instead of the whole screen, so that the toolbar remains visible?
Yes, go to "Settings" -> "Data Types" and select your rich text editor (or if you are using the default one then select "Richtext editor").
Scroll down to "Dimensions". Here you can set the height (and leave the width empty) Click "Save"
But keep in mind, if you change the default one then it will change it for all "Document Types" that are using it. So maybe it is better to create a new "Data Type".