There are a few ways:
Try using the Direction-Distance point construction tool:
With point snapping turned on, Create Features pane > Any point layer > Point tool > on the toolbar that appears on the map, choose the Direction Distance construction tool > Snap to the existing point while setting the direction and distance.
https://pro.arcgis.com/en/pro-app/2.7/help/editing/create-a-point-or-vertex-at-a-direction-and-dista...
Another way, use the Point At End Of Line tool while snapping to the existing point:
https://pro.arcgis.com/en/pro-app/latest/help/editing/create-point-and-multipoint-features.htm#GUID-...
Constrain the temporary line segment to a specific length by setting a Distance constraint:
https://pro.arcgis.com/en/pro-app/latest/help/editing/constrain-distance-for-a-segment.htm