Wella Toner for Dark Blonde Hair with highlights?

We don't tend to recommend the use of that toner on this forum as it has to be mixed with peroxide. Most of us either use purple conditioner, leaving it for 10-30 minutes before rinsing or diluting a darker purple dye with conditioner.

Thanks for the reply Allie. Maybe I'll try the diluted Manic Panic again then. I definitely don't want to damage my hair more. I also just ordered Shu Uemura Color Lustre Shades Reviving Balm in cool blonde because it has really good reviews and people said it worked for them when other purple shampoos/conditioners didn't. It was really expensive, so I hope it works.

use one of the dark purple conditioners - don't bother with purple shampoos. Open the conditioner lid and look inside and see how dark it is - darker = better. Shampoo hair then put the conditioner in. Might need to experiment with time like 10 min to start. Anyway, it's good for your hair. I've had really good results with Roux White Minx hair rinse also possible to get as mousse at some stores. I find it at Sally's. Wash hair, then put this stuff in, don't rinse out. It made my brassy hair nearly white platinum and also smooth. BUT , it washes out. But I only wash my 1-2 times/wk so it's not a big deal to use this product that often.

Purple shampoos can actually be very effective. The secret is to apply them evenly to dry hair and leave on for up to half an hour

I have wondered about these for years. I went ahead and finally used a wella toner yesterday T 18 Specifically. I ended up with grey despite only leaving it on for twenty minutes when the instructions say thirty.  The damage wasn't terrible but I baby my platinum hair anyway.  I will say this stuff smells worse then bleach.  It smells like amonia which cannot be good for your hair. 

In any case it turned my hair from the pale banana yellow to a silvery grey. I will post a picture once I upload one.
I am ok with it and think it will fade to white which was my goal but for what you seem to be looking for I would probably go with one of the other options first because they are ultimately less damaging.