I often use voting up a question as a way to essentially 'bookmark' a question or an answer that I can refer to later. The only issue I may run into though is that it can often be hard to tell if a question was from Security or Crypto or Stackoverflow etc--so with this, is there any central location I can view my voting history from all different exchanges simultaneously?
To answer your question
I don't believe it's possible.
Your network profile has various information about your activity on all Stack Exchange sites, but not voting.
I often use voting up a question as a way to essentially 'bookmark' a question or an answer that I can refer to later
While reasons for voting are entirely personal choice and up to us individually, can I ask you to please consider not voting as a way of bookmarking?
This provides false feedback for others in search results and when viewing a question or answer and expecting it to be of a certain quality based on the votes. Not expecting users to be voting to "bookmark".
Your voting history is not even a very useful mechanism to be using for this.
How can you easily and quickly find questions and answers of interest, if you have to trawl all your upvote history, which is not ordered in any way useful for "bookmarking"?
How do you differentiate between posts you've upvoted because of quality, and posts you've upvoted for bookmarking reasons?
Does your using voting as a mechanism for bookmarking deter you from upvoting for quality purposes so you only have votes in your history for questions you want "bookmarked"?
If so, then the site is losing valuable votes from you, and if not, it's just another reason why this is not the ideal approach.
If posts are deleted which you had upvoted (or "bookmarked") you will never know, and could spend ages looking through all your votes on different sites you are registered on, across months of vote history.
You will not have any confirmation "this bookmark is gone", you just will never find it.
Whereas with browser bookmarks (or another method) you would click the bookmark and be show a Stack Exchange site's page stating "not found" or "no longer exists" etc.
Then you can delete the bookmark.
You could make use of the site's "favourite" questions function.
Then you have the added bonus of seeing your favourites on all sites from your network profile:
A better solution would be to use your browser bookmarking. Create a new folder in your bookmarks called "Stack", then sub folders in "Stack" of whatever sorts of things you bookmark. e.g. "Interesting" or "Git" or "Nodejs" etc. Then save the questions/answers you find useful in there.
You can even have sub folders for each site of interest, and add a new folder for a site if you join a new one one.
This also allows you to bookmark an answer directly, as you can select the "share" link on the answer, paste it into your browser and click go, then bookmark that page and the browser will bookmark the page with the URL of the answer.
Loading that bookmark in the future will take you directly to the answer, as opposed to just being taken to the question and having to trawl through all answers to find and remember why you bookmarked that thread.
In either case, or another option, you can then vote for the right reasons (quality, useful, etc) and "bookmark" separately :)