In reply to Inhambane:
Generally, yes. Especially if it’s actual training - at least some vague structure as opposed to half heartedly doing random things on random days. However everyone’s circumstances will be different. How useful indoor training will be depends on a multitude of factors:
The type(s) of climbing you do
Your current level outdoors
The level you aspire to outdoors
How often you climb outdoors
How long you’ve been climbing / training
How good your technique is
Your natural strengths and weaknesses eg good strength to weight ratio, stamina, finger strength.
Do you pick routes that suit you, eg slabby stuff which rewards footwork and finger strength but doesn’t require other physical attributes
etc etc