Techniques are described for facilitating access of computing system users to restricted or other functionality, such as internal functionality of a business or other organization. The functionality access may be facilitated by an access provider system that executes on a client computing system of an authorized user, such as a program operating in conjunction with another presentation program that presents publicly available information by modifying interactions available to the user when using the presentation program or otherwise providing additional information to the user. In some situations, the additional information is provided by temporarily modifying the information being presented by the presentation program, such as to provide additional information that is related to functionality corresponding to a subject area of the currently presented information and/or corresponding to an aspect of the currently presented information that is indicated by the user.