The Shulhan Aruch in SIman 679:3 discusses a candelabra lit before Shabbat. Since the candles were lit through Ben HaShmashot (twilight), the candlesticks remain Mukse as a “Basees” (base) even after the flames are extinguished. Maran cites an opinion that if a non-Mukse object, such as bread, is placed on the candelabra as well, the candelabra will not be Mukse. This is based on the principle that a “Basees” (base) which not only holds the Mukse (flame), but the non-Mukse food item, as well, does not become Mukse. Nevertheless, Maran rules in accordance with the Rivash that one should not rely on that opinion, since the flame will always be considered more important than the bread during Ben HaShmashot, as the flame is needed for the Misva of Shabbat candles. The Magen Abraham and the Mishna Berura bring another reason why the bread does not neutralize the candelabra from becoming Mukse. They argue that since the candelabra is inherently designed to hold the lit candle, it will always be considered a base for it, and not for the extraneous bread. Thus, for these two reasons, there is no way to prevent the candelabra from becoming Mukse for the entire Shabbat.
Hacham Bension writes in a note to Ohr Lesion (2:18, Responsa 21) that if the piece of bread placed on the candelabra is “Chashuv”-(significant), it can prevent the candelabra from becoming Mukse. However, this is problematic, as Maran clearly indicates that no type of bread will be of use in this case.
This discussion has dealt with the candelabra. However, the Poskim also discuss a candelabra placed on a tray. The question is whether placing a piece of bread or jewelry on the tray will counteract the tray from becoming Mukse as a “Basees” to the candelabra. Rav Shlomo Zalman Auerbach (Jerusalem, 1910-1995) was lenient and held that it is different than the candelabra. As opposed to the candelabra, the tray is multifunctional and is also considered a base for the bread or jewelry. Likewise, the tray is not a base for the flame itself, which is the critical Misva, but for the base of the flame, i.e. the candelabra. Accordingly, the tray may be moved with the candelabra and non-Mukse item, after the flame goes out, if the space it occupies is needed. Rav Elyashiv (Jerusalem, 1910-2012) was also lenient, but added a caveat that one must always leave a permitted item on the tray every week, to demonstrate that indeed the tray is meant for that.
A candelabra lit from before Shabbat, will remain Mukse the entire Shabbat, even after the flames have gone out. Placing bread on the candelabra will not change the status of the candelabra. However, if the candelabra is on a tray, placing bread or jewelry on the tray will allow the tray to be moved for its space, once the candles are extinguished.