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If you receive a new version of an indicator and want to install it into ThinkOrSwim (TOS), the indicator file name may be the same as the old one. 

"I'm installing a new version of an indicator / study. Do I need to remove the old version before I install the new one? I get a message asking if I want to replace the indicator." 

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Unless you have a specific reason to keep the prior version of an indicator, Click Yes.

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A very common case of this is the Voodoo lines where updates to the indicator regularly come out. 

If you try to import a newer version / updated indicator file and you recieve the following message, 

"Do you really want to replace ST_NameOfStudy by file...."

Go ahead and click "Yes" to replace the file. 

If for some reason you want to keep the old file along with the new one, you will need to rename one of them.  

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How to update Voodoo Lines in ThinkorSwim
​https://intercom.help/simpler-trading/en/articles/3347514

TOS indicator will not import
​https://intercom.help/simpler-trading/en/articles/3481530